LED display are widely used in various applications in nowadays, such as displays for stage background and scrolling signs for advertising. Though LEDs are characterized by having a long service life, they do eventually fail. Testing the bulbs in these displays will help troubleshoot a malfunctioning display circuit. The test procedures for one color and full color led display are the same. See as below:

1. Review the data sheet for the display. This document will reveal important information such as which pins are anodes and cathodes, which are respectively the positive and negative leads. You should also find out whether the display is common anode or common cathode, meaning that multiple LEDs in the display either have their positive or negative leads all tied together to a pin.

2. Turn on and set up the multimeter for diode testing. Following the instructions specific to the multimeter being used, select the diode tester function.

3. Connect the multimeter leads to two of the pins of the display. The positive lead should clip onto an anode, while the negative lead clips to a respective cathode.

4. Observe the LED display. Upon making a connections to the anode and cathode, you should see at least one LED illuminate. Remove the leads after each test, and repeat this procedure until all LEDs in the display have been checked. If you do not see light emitting from the element connected, then that LED is not working. Based upon whether all the LEDs in the display function, determine if it should be used or discarded.